Muffler

ABSTRACT

Gas flow induced by a pulsating pressure source such as an internal combustion engine, is conducted through a main duct having an acoustical impedance created by parallel branched, resonator chambers acting as low pass filters to gate low frequency pressure pulsations while absorbing higher frequency acoustical energy. Angled connecting passages between the main duct and the resonator chambers impart spin to the gas and create turbulent conditions for sonic wave transmission. This invention relates to noise abatement devices or mufflers of the wave filter type.

[ Dec. 18, 1973 United States Patent [1 1 Johnson 3,243,01! 3/l966Hill.............

[ MUFFLER [76] Inventor:

n 0 ms nle RM .1 Wn 0 G mF n mh .10 4 r e mm im ma a mm m PA Howard R.Johnson, 3300 Mt. Hope Rd., Grass Lake, Mich. 49240 June 2, 1972 Appl.No.: 258,988

Attorney-Harvey B. Jacobson [22] Filed:

[57] ABSTRACT Gas flow induced by a pulsating pressure source such as aninternal combustion engine, is conducted through a main duct having anacoustical impedance created by parallel branched, resonator chambersacting as low pass filters to gate low frequency pressure pulsationswhile absorbing higher frequency acoustical energy. Angled connectingpassages between the main 98 00 50 4 9 oo 9 .m 7 omm7 6 ,5R 87 mw1 8 m74m. o 1 8F 00 1 m h c r. 8 ue US .L Hf C d SLd UmF HUT 555 [ll [5 6]References Cited UNITED STATES PATENTS duct and the resonator chambersimpart spin to the r m o w m c .w w n e 0 d S t r n S 0 e e S e g n m.I. .m b F .n a ma .0 .I m .mmw c o a n r m U Sf m m avi w aa [Wu m T mr n VS i r mmme s swmm a UTm 8868 4465 HHHH 8888 5 JJWM T Pigman .m X aM McCurdy..;...........................

m ymm m r mc u C MDM 94822 402346 999999 HHHHHH 53 26 l l MUFFLER Theuse of side branch acoustical wave filters for attenuating certainsound'frequencies, known to exist in the exhaust conduits of internalcombustion engines, is well known as disclosed for example, in US. Pat.No. 1,910,672- to Bourne. Such wave filters include side branchresonator chambers connected to a main flow duct by communicatingorifices or necks that are short I in comparison with the wave lengthsof the pulsations dealt with.

As a general practice in noise abatement, flow discontinuities such asthe aforementioned side branch type are used to increase acousticalimpedance by wave reflection and interference in the main flow duct withwhich the discontinuity is associated so that only a small fraction ofthe acoustical energy exits with the gas. Where the side branch flowarea is equal to or less than that of the main duct,the impedance issuch that relatively narrow stop frequency bands are established.Further, if the side branch duct is closed, it also acts as a low passfilter while the impedance at one of the stop frequency bands approachesinifity where the closed duct included a resonator chamber to effectrelatively large sound absorption in the stop band embracing theresonant frequency. Thus, a wave filter may be constructed in accordancewith well known acoustical the-.

ory and supporting empirical data, to suppress only the undesirablehigher frequency pulsations in a flow stream of gas without appreciablyaffecting the lower frequency pulsations. Harmonic analysis of flow inthe intake or exhaust conduits of a pulsating pressure source, such asan internal combustion engine, show that alternating fiow at severaldifferent higher frequencies are superimposedon the lower unidirectionalflow-inducing frequencies of the pressure pulsations and it is thesehigher frequencies that suffer attenuation by resonator types of sidebranch wave filters in accordance with the present invention.

The thermal efficiency of a suitable wave filter of the aforementionedtype having a low pass frequency characteristic anda cut-off frequencyrange, was heretofore unsatisfactory for internal combustion enginemuffler installations because of size limitations. In accordance withthe present invention, however, the thermal efficiency is significantlyimproved by initially baffling flow to create turbulence and imparting aspin to the gas within the resonator chambers along an arcuate flowpassage, to effect a substantial reduction in size. Despite this spin,the gas can exit the resonator chambers and reenter the main flow streambecause of the fact that the internal combustion engine operates as achemical batch process.

The spin of the gas is produced by the orientation of side branchconnecting passages at an acute angle in the direction of flow relativeto the main flow stream and the circular configuration of the resonatorchambers disposed in tangential relation to the connecting passages. Theangular orientation of each connecting passage creating a maximumcoriolis effect on the flowing gas and its converging flow area,enhances the spinning action or vortical motion produced. The spinningmotion imparted to the gas provides turbulent conditions fortransmission of the sound waves and lowers gas temperature which is afunction of the acoustical velocity. Thus, pressure pulsations from theinternal engine, enhanced by the spinning effect on the gas achieves agating action from each resonator chamber comparable to the phenomenonin a pulse jet engine wherein cyclic combustion at sonic frequenciesunidirectionally gates the inflow of air through the exhaust nozzle.

These together with other objects and advantages which willbecomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout and in which: I

FIG. 1 is a perspective view showing one embodiment of and installationfor the present invention.

FIG. 2 is a top sectional view taken substantially through a planeindicated by section line 22 in FIG. 1.

FIG. 3 is a vertical sectional view taken substantially through a planeindicated by section line 33 in FIG.

FIG. 4 is a schematic illustration of the basic wave filter structureassociated with the present invention.

Referring now to the drawings in detail, FIG. 1 shows a typicalinstallation of a muffler device 10 between an exhaust conduit 12 from apulsating pressure source such as an internal combustion engine, and atail pipe 14 connected to a discharge pressure region or. atmosphere. Inthe illustrated embodiment, the muffler device includes a cylindricalhousing 16 closed at one axial end by the cover 18 and at the otheraxial end by an end wall 20 to which the tail pipe is connected by elbowportion 22. The conduit 12 is connected to the housing in substantiallytangential relation by the connector formation 24.

As shown in FIGS. 2 and 3, the muffler device includes a rigid corestructure generally denoted by reference numeral 26 that is fixedinternally within the housing by the assembly bolts 28 that also holdthe cover 18 assembled with the housing 16 to seal the interior thereof.A main flow duct or channel is formed within the housing by the corestructure including a peripherally outer circular portion 32 connectedin series with an inner circular portion 34 as more clearly seen in FIG.2. The inlet end 36 of the fiow duct communicates with the conduit 12while the outlet end 38 opens into an axial outlet chamber 40 centrallylocated within the housing in communication with the outlet elbow 22through the bottom wall 20.

The main duct 30 constitutes a flow passage for gas conducted in onedirection as indicated by the main flow stream arrows 42. Baffle meansincluding a baffle chamber 44 is formed within the core structureadjacent to the inlet end 36 of the duct, into which a portion of theflow stream is diverted to impart some spinning motion thereto andthereby initially establish some turbulence in the main gas flow stream.The main flow passage in duct 30, following the baffle chamber, isprovided with a plurality of wave filter types of discontinuities 46 atspaced locations along both portions 32 and 34 of the duct in order tocreate the desired acous- 1 tical impedance for noise abatementpurposes.

As more clearly seen in FIG. 4, each of the discontinuities or wavefilter formations 46 includes a resonator chamber or cavity 48 ofcircular configuration that is volumetrically enlarged relative to anassociated side branch duct or connecting passage 50 tangentiallyconnected to ,the resonatorchamber. The side branch duct the convergenceof its flow passage in the direction of 5 flow and its tangentialrelationship to the resonator chamber 48, imparts a spinning motion tothe gas entering and exiting from the resonator chamber.

In accordance with acoustical wave filter theory and practice asaforementioned, the branch duct 50 is made shorter in length than thewavelengths of the lowest pressure pulsations dealt with. Further, themaximum flow area (b) of the branch duct is equal to or less than theflow area (a) of the main duct 30. The acoustical wave filter 46 isthereby designed to suppress the objectionable noise producing,alternating pulsations at the higher frequencies while gating orpermitting the low frequency, unidirectional flow pulsations to pass.Since the wave filters are associated with the flow of hot gas from aninternal combustion engine, the spinning motion imparted to the gas bythe unique configuration and arrangement of the wave filters 46 accountsfor a thermal efficiency for this type of muffler device that makes itpractical for the size limitations of installations including two cycleengine as well as diesel engine power plants.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modificationsand equivalents maybe resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. In combination with a source of pressure pulsating at relativelylower frequencies and a conduit connected to said source through which aflow of gas is induced by said pulsating pressure, wave filter means forreducing noise produced by sonic pulsations at relatively higherfrequencies, comprising elongated passage means connected to the conduitfor establishing a flow path for said gas between said source and adischarge pressure region, resonator chamber means connected to thepassage means for establishing substantially infinite acousticalimpedance at said higher frequencies, gas spin means responsive to flowof the gas between the passage means and the resonator chamber means forimparting vortical motion thereto, and means for initially impartingturbulence to the gas entering the passage 'means from the conduit.

2. The combination of claim 1 wherein said passage means includes ahousing to which the conduit is connected and a core fixed internallywithin the housing forming an elongated main duct, the resonator meansand the gas spin means being formed within the core.

3. The combination of claim 2 wherein said gas spin means includes abranch duct extending from the passage means at an acute angle in thedirection of flow and connected tangentially to the resonator chambermeans.

4. The combination of claim 3 wherein said resonator chamber meansincludes at least one closed cavity enclosing a volume larger than thebranch duct, the branch duct having a cross-sectional flow area that isless than that of the passage means.

5. The combination of claim 4 wherein said main duct includesperipherally outer and inner arcuate portions connected in series, theouter portion having an inlet end connected to the conduit and the innerportion having an outlet end.

6. The combination of claim 1 wherein said passage means-includes aradially outer inlet end, a radially inner outlet end, and an arcuateduct interconnecting the inlet and outlet ends.

7. In combination with a source of pressure pulsating at relativelylower frequencies and a conduit connected to said source through which aflow of gas is induced by said pulsating pressure, wave filter means forreducing noise produced by sonic pulsations at relatively higherfrequencies comprising elongated passage means connected to the conduitfor establishing a flow path for said gas between said source and adischarge pressure region, resonator chamber means connected to thepassage means for establishing substantially infinite acousticalimpedance at said higher frequencies, gas spin means responsive to flowof the gas between the passage means and the resonator chamber means forimparting vortical motion thereto, said passage means including ahousing to which the conduit is connected and a core fixed internallywithin the housing forming an elongated main duct, the resonator meansand the gas spin means being formed within the core.

8. The combination of claim 7 wherein said resonator means comprises aplurality of closed cavities connected in parallel to said main duct bythe gas spin means.

9. The combination of claim 7 wherein said resonator chamber meansincludes at least one closed cavity connected to the passage means bythe gas spin means.

1. In combination with a source of pressure pulsating at relativelylower frequencies and a conduit connected to said source through which aflow of gas is induced by said pulsating pressure, wave filter means forreducing noise produced by sonic pulsations at relatively higherfrequencies, comprising elongated passage means connected to the conduitfor establishing a flow path for said gas between said source and adischarge pressure region, resonator chamber means connected to thepassage means for establishing substantially infinite acousticalimpedance at said higher frequencies, gas spin means responsive to flowof the gas between the passage means and the resonator chamber means forimparting vortical motion thereto, and means for initially impartingturbulence to the gas entering the passage means from the conduit. 2.The combination of claim 1 wherein said passage means includes a housingto which the conduit is connected and a core fixed internally within thehousing forming an elongated main duct, the resonator means and the gasspin means being formed within the core.
 3. The combination of claim 2wherein said gas spin means includes a branch duct extending from thepassage means at an acute angle in the direction of flow and connectedtangentially to the resonator chamber means.
 4. The combination of claim3 wherein said resonator chamber means includes at least one closedcavity enclosing a volume larger than the branch duct, the branch ducthaving a cross-sectional flow area that is less than that of the passagemeans.
 5. The combination of claim 4 wherein said main duct includesperipherally outer and inner arcuate portions connected in series, theouter portion having an inlet end connected to the conduit and the innerportion having an outlet end.
 6. The combination of claim 1 wherein saidpassage means includes a radially outer inlet end, a radially inneroutlet end, and an arcuate duct interconnecting the inlet and outletends.
 7. In combination with a source of pressure pulsating atrelatively lower frequencies and a conduit connected to said sourcethrough which a flow of gas is induced by said pulsating pressure, wavefilter Means for reducing noise produced by sonic pulsations atrelatively higher frequencies comprising elongated passage meansconnected to the conduit for establishing a flow path for said gasbetween said source and a discharge pressure region, resonator chambermeans connected to the passage means for establishing substantiallyinfinite acoustical impedance at said higher frequencies, gas spin meansresponsive to flow of the gas between the passage means and theresonator chamber means for imparting vortical motion thereto, saidpassage means including a housing to which the conduit is connected anda core fixed internally within the housing forming an elongated mainduct, the resonator means and the gas spin means being formed within thecore.
 8. The combination of claim 7 wherein said resonator meanscomprises a plurality of closed cavities connected in parallel to saidmain duct by the gas spin means.
 9. The combination of claim 7 whereinsaid resonator chamber means includes at least one closed cavityconnected to the passage means by the gas spin means.